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dmarc=pass (p=quarantine dis=none) header.from=poczta.fm Authentication-Results: smtp.kernel.org; spf=pass smtp.mailfrom=poczta.fm Received: from nr200 (unknown [80.68.231.31]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-256) server-digest SHA256) (No client certificate requested) by poczta.interia.pl (INTERIA.PL) with ESMTPSA; Wed, 29 Jul 2026 08:27:35 +0200 (CEST) Date: Wed, 29 Jul 2026 08:27:32 +0200 From: Slawomir Stepien To: Konstantin Komarov , ntfs3@lists.linux.dev Cc: syzbot , syzkaller-bugs@googlegroups.com, linux-kernel@vger.kernel.org, syzbot@lists.linux.dev, syzkaller-upstream-moderation@googlegroups.com Subject: Re: [PATCH] fs/ntfs3: handle partial allocation in attr_data_get_block_locked() Message-ID: References: <8fc44517-e231-4539-a353-3dd47045a203@mail.kernel.org> Precedence: bulk X-Mailing-List: syzbot@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8fc44517-e231-4539-a353-3dd47045a203@mail.kernel.org> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=poczta.fm; s=dk; t=1785306456; bh=j71uMXwnOK6KYMsp07xsuBtAPsDk19Ch/WVHo7qdZGo=; h=Date:From:To:Subject:Message-ID:MIME-Version:Content-Type; b=TlvKdnkXl0dGl+OaMVf5m0kea2CCouriNQCOJ6i7PLBBecZA0BJpQd/rsCKozaeup E27wVyMZCIYNT9UOlzr7gVWsVyZupcOaRuX5JbCx0C4vfXNTIpbxCh9DHWVJz20Nfp TMMcobVekCQcXBII2cqn9I9Kia08f0WQCxnFElxo= Hello A gentle reminder about this PATCH. On lip 15, 2026 12:29, syzbot wrote: > From: Slawomir Stepien > > When allocating clusters for a sparse or compressed attribute in > attr_data_get_block_locked(), the requested virtual cluster number (vcn0) > is aligned down to a frame boundary (vcn). The function then attempts to > allocate a full frame of clusters. > > If the disk is nearly full and highly fragmented, attr_allocate_clusters() > might only manage to allocate a small fragment and return success with a > partial allocation length. If this partial allocation is so small that it > does not even reach the originally requested vcn0 (i.e., end <= vcn0), vcn0 > remains unallocated (a sparse hole). > > When the code subsequently calls run_lookup_entry() for vcn0, it finds the > original SPARSE_LCN entry, which triggers a WARN_ON(1). > > Fix this by adding a check to verify if the partial allocation reached > vcn0. If it did not (vcn0 >= end), treat this as an -ENOSPC failure and > jump to the undo1 label. This safely rolls back the partial allocation, > restores the original size, and repacks the runs, leaving the inode in a > consistent state before returning the error to the caller. > > WARNING: fs/ntfs3/attrib.c:1236 at attr_data_get_block_locked+0x1980/0x25d0 > fs/ntfs3/attrib.c:1236 > RIP: 0010:attr_data_get_block_locked+0x1980/0x25d0 fs/ntfs3/attrib.c:1236 > Call Trace: > > attr_data_get_block+0x1f1/0x2a0 fs/ntfs3/attrib.c:979 > ntfs_fallocate+0xd3d/0xf70 fs/ntfs3/file.c:670 > vfs_fallocate+0x663/0x7f0 fs/open.c:338 > ksys_fallocate fs/open.c:362 [inline] > __do_sys_fallocate fs/open.c:367 [inline] > __se_sys_fallocate fs/open.c:365 [inline] > __x64_sys_fallocate+0xbf/0x110 fs/open.c:365 > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] > do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > > Fixes: 099ef9ab9203 ("fs/ntfs3: implement iomap-based file operations") > Assisted-by: Gemini:gemini-3.1-pro-preview Gemini:gemini-3-flash-preview syzbot > Reported-by: syzbot+7be6ad5cb228286af3e3@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=7be6ad5cb228286af3e3 > Link: https://syzkaller.appspot.com/ai_job?id=3c9dee6e-001d-4972-8bf6-f6c960708246 > Signed-off-by: Slawomir Stepien > > --- > diff --git a/fs/ntfs3/attrib.c b/fs/ntfs3/attrib.c > index c621a4c58..786fd0ec0 100644 > --- a/fs/ntfs3/attrib.c > +++ b/fs/ntfs3/attrib.c > @@ -1227,6 +1227,10 @@ int attr_data_get_block_locked(struct ntfs_inode *ni, CLST vcn, CLST clen, > total_size = total_size0 + ((u64)*len << cluster_bits); > > if (vcn != vcn0) { > + if (vcn0 >= end) { > + err = -ENOSPC; > + goto undo1; > + } > if (!run_lookup_entry(run, vcn0, lcn, len, NULL)) { > err = -EINVAL; > goto out; > > > base-commit: 8cdeaa50eae8dad34885515f62559ee83e7e8dda -- Slawomir Stepien